thermal: rcar: Fix race condition between init and interrupt

As soon as the interrupt has been enabled by devm_request_irq(), the
interrupt routine may be called, depending on the current status of the
hardware.

However, at that point rcar_thermal_common hasn't been initialized
complely yet. E.g. rcar_thermal_common.base is still NULL, causing a
NULL pointer dereference:

    Unable to handle kernel NULL pointer dereference at virtual address 0000000c
    pgd = c0004000
    [0000000c] *pgd=00000000
    Internal error: Oops: 5 [#1] SMP ARM
    CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.19.0-rc7-ape6evm-04564-gb6e46cb7cbe82389 linux-sunxi#30
    Hardware name: Generic R8A73A4 (Flattened Device Tree)
    task: ee8953c0 ti: ee896000 task.ti: ee896000
    PC is at rcar_thermal_irq+0x1c/0xf0
    LR is at _raw_spin_lock_irqsave+0x48/0x54

Postpone the call to devm_request_irq() until all initialization has
been done to fix this.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/rcar_thermal.c

@@ -387,21 +387,9 @@ static int rcar_thermal_probe(struct platform_device *pdev)
 
 	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 	if (irq) {
-		int ret;
-
 		/*
 		 * platform has IRQ support.
 		 * Then, driver uses common registers
-		 */
-
-		ret = devm_request_irq(dev, irq->start, rcar_thermal_irq, 0,
-				       dev_name(dev), common);
-		if (ret) {
-			dev_err(dev, "irq request failed\n ");
-			return ret;
-		}
-
-		/*
 		 * rcar_has_irq_support() will be enabled
 		 */
 		res = platform_get_resource(pdev, IORESOURCE_MEM, mres++);
@@ -456,8 +444,16 @@ static int rcar_thermal_probe(struct platform_device *pdev)
 	}
 
 	/* enable temperature comparation */
-	if (irq)
+	if (irq) {
+		ret = devm_request_irq(dev, irq->start, rcar_thermal_irq, 0,
+				       dev_name(dev), common);
+		if (ret) {
+			dev_err(dev, "irq request failed\n ");
+			goto error_unregister;
+		}
+
 		rcar_thermal_common_write(common, ENR, enr_bits);
+	}
 
 	platform_set_drvdata(pdev, common);